FIG. 17 shows a base station and user terminals in MU-MIMO (Multiple User-Multiple Input Multiple Output) architecture. As shown in FIG. 17, the user number K is variable since the coverage area of one base station is fixed and the users are not fixed. The size of matrix for the precoding matrix generator is determined by the user number K.
Matrix inversion (MI) is widely used in signal processing, especially in the wireless communication area. In some cases, the size of the matrix for MI processing is variable.
For example, in the MU-MIMO technology, the zero-forcing (ZF) precoding involves the calculation as shown in the equation (Math.1).W=HH(HHH)−1  [Math. 1]
In the equation (Math.1), W is the precoding matrix, H is the channel matrix. The size of H is variable according to the number of involved users.
Patent Literature 1 (PTL1) discloses a channel matrix calculation device for efficiently performing the inverse matrix calculation operation of a channel matrix by systematization. According to Patent Literature 1, a channel matrix calculation device enables a transmission/reception antenna to be compatible with an M×N system in a multi-carrier system MIMO system.
Patent Literature 2 (PTL2) discloses another channel matrix calculation device which can calculate channel matrixes of all subcarriers within an OFDM (Orthogonal Frequency Division Multiplexing) symbol period and enables transmission reception antennas to be adaptive to an M×N system.
Patent Literature 3 (PTL3) discloses a recursive calculation method of the channel matrix for the MIMO equalizer. Patent Literature 4 (PTL4) discloses a technique for relatively accurately detecting positional displacement between plural images while suppressing an operation load.
[PTL 1]
    Japanese Patent Laid-open Publication No. JP-2007-13455A[PTL 2]    Japanese Patent Laid-open Publication No. JP-2006-229436A[PTL 3]    Japanese Patent Laid-open Publication No. JP-2009-524291A[PTL 4]    Japanese Patent Laid-open Publication No. JP-2012-123652A